Fan having an impeller including a resin portion and a metal plate

ABSTRACT

A fan includes an impeller and a metallic base portion. The base portion is arranged to be in thermal contact with a heat source. The impeller includes a resin portion including a plurality of blades, and a metal plate. In addition, the metal plate includes a flat plate portion arranged below the blades. A lower surface of the flat plate portion and an upper surface of the base portion are arranged axially opposite to each other with a gap intervening therebetween. An axial dimension of the gap is arranged to be 200 μm or less at least at a portion of the gap. Heat of the heat source is transferred to the metal plate through radiation from the base portion. Then, an air current produced by the impeller absorbs the heat from the metal plate. The heat generated from the heat source is thus efficiently discharged to an outside.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a centrifugal fan.

2. Description of the Related Art

Centrifugal cooling fans are typically installed in electronic devices,such as computers, to cool electronic components. Such a cooling fan isarranged to rotate an impeller to produce an air current travelling in acentrifugal direction. An electronic component inside the electronicdevice is thus cooled by the air current. The air current produced bythe impeller is sometimes used to cool a circuit designed to drive thecooling fan. A known cooling fan is described in, for example, US2011/0103011.

In recent years, electronic devices have been becoming more and moresophisticated in functionality, and there has accordingly been a demandfor improved cooling performance of blower fans. US 2011/0103011describes a heat exchanger 2100 including a heat transfer structure 2105and a heat conducting structure 2110. In the heat exchanger 2100, a. CPU2120, which is a heat source, is arranged inside the heat conductingstructure 2110. Heat of the CPU 2120 is discharged to an outside throughthe heat transfer structure 2105, which is made of a metal.

To increase heat dissipation efficiency of the heat exchanger 2100described in US 2011/0103011, an air volume needs to be increased byincreasing the rotation rate of the heat transfer structure 2105.However, the heat transfer structure 2105 of the heat exchanger 2100described in US 2011/0103011 is entirely made of the metal. Accordingly,the heat transfer structure 2105 has a great weight, and it is thereforedifficult to increase the rotation rate of the heat transfer structure2105 to increase the volume of the air current.

SUMMARY OF THE INVENTION

A fan according to a preferred embodiment of the present inventionincludes a motor, an impeller, a base portion, and a heat source. Themotor is arranged to produce a torque centered on a central axisextending in a vertical direction. The impeller is arranged to rotatethrough the torque to blow air in a centrifugal direction. The baseportion is made of a metal, and is arrange to extend perpendicularly tothe central axis below the impeller to support the motor. The heatsource is arranged to be in thermal contact with the base portion. Theimpeller includes a resin portion and a metal plate. The resin portionincludes a blade support portion directly or indirectly fixed to arotating portion of the motor, and a plurality of blades arrangedradially outside of the blade support portion. The metal plate includesa flat plate portion arranged below the plurality of blades. A portionof the metal plate is covered with a resin of the resin portion. A lowersurface of the flat plate portion and an upper surface of the baseportion are arranged axially opposite to each other with a gapintervening therebetween. An axial dimension of the gap is arranged tobe 200 μm or less at least at a portion of the gap.

According to the above, preferred embodiment of the present invention, aportion of the impeller is made of a resin to reduce the weight of theimpeller, and to make it possible to efficiently discharge heatgenerated from the heat source to an outside.

The above and other features, elements, steps, characteristics andadvantages of the present invention will become more apparent from thefollowing detailed description of preferred embodiments of the presentinvention with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top view of a fan according to a preferred embodiment of thepresent invention.

FIG. 2 is a vertical cross-sectional view of the fan according to theabove preferred embodiment of the present invention.

FIG. 3 is a vertical cross-sectional view of a sleeve according to theabove preferred embodiment of the present invention.

FIG. 4 is a top view of an impeller according to the above preferredembodiment of the present invention.

FIG. 5 is a top view of a metal plate according to the above preferredembodiment of the present invention.

FIG. 6 is a partial vertical cross-sectional view of the fan accordingto the above preferred embodiment of the present invention.

FIG. 7 is a partial vertical cross-sectional view of a fan according toa modification of the above preferred embodiment of the presentinvention.

FIG. 8 is a vertical cross-sectional view of a fan according to amodification of the above preferred embodiment of the present invention.

FIG. 9 is a vertical cross-sectional view of a fan according to amodification of the above preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, preferred embodiments of the present invention will bedescribed with reference to the accompanying drawings. It is assumedherein that a direction parallel or substantially parallel to a centralaxis of a motor which drives a fan is referred to by the term “axialdirection”, “axial”, or “axially”, that directions perpendicular orsubstantially perpendicular to the central axis of the motor are eachreferred to by the term “radial direction”, “radial”, or “radially”, andthat a direction along a circular arc centered on the central axis ofthe motor is referred to by the term “circumferential direction”,“circumferential”, or “circumferentially”. It is also assumed in thefollowing preferred embodiments that an axial direction is a verticaldirection, and that a side on which an impeller is arranged with respectto a base portion is defined as an upper side. The shape of each memberor portion and relative positions of different members or portions willbe described based on the above assumptions. It should be noted,however, that the above definitions of the vertical direction and theupper side are not meant to restrict in any way the orientation of a fanaccording to any preferred embodiment of the present invention when inuse.

FIG. 1 is a top view of a fan 1 according to a preferred embodiment ofthe present invention. FIG. 2 is a vertical cross-sectional view of thefan 1. The fan 1 is a blower arranged to produce an air current throughrotation of an impeller 30 caused by power of a motor 20. The fan 1 is,for example, installed in an electronic device, such as, for example, acomputer, to cool an electronic component. Note that the fan 1 accordingto the present preferred embodiment may be installed in a device otherthan the electronic device. Fans according to preferred embodiments ofthe present invention may be installed in, for example, householdelectrical appliances, medical appliances, transportation equipment, orthe like.

Referring to FIGS. 1 and 2, the fan 1 according to the present preferredembodiment includes a base portion 10, the motor 20, and the impeller30.

The base portion 10 is as metallic plate-shaped member arranged tosupport the motor 20. The base portion 10 is arranged below the impeller30. In addition, the base portion 10 is arranged to extendperpendicularly to a central axis 9. The base portion 10 is fixed to aframe of a device to which the fan 1 is attached through, for example,screws. Aluminum or an aluminum alloy, for example, is used as amaterial of the base portion 10. Note that the base portion 10 may bemade of a material other than aluminum and the aluminum alloy.

A side wall portion 11 is arranged on a peripheral portion of an uppersurface of the base portion 10. The side wall portion 11 is arrangedradially outside of the impeller 30, and is arranged to extend in acircumferential direction around the impeller 30. An outlet 111 for agas is defined between both circumferential end portions of the sidewall portion 11. In addition, the side wall portion 11 includes a guideprojection 112 arranged to project between the impeller 30 and theoutlet 111. The fan 1 according to the present preferred embodiment isarranged along an inside surface of a case 90 of the device to which shefan 1 is attached. While the fan 1 is running, the gas is taken into thefan 1 inside the case 90 through an opening 91 defined in the case 90.

The motor 20 is a source of power to rotate the impeller 30. The motor20 includes a stationary portion 40 and a rotating portion 50. Thestationary portion 40 is fixed to the base portion 10. The rotatingportion 50 is supported to be rotatable with respect to the stationaryportion 40. Referring to FIG. 2, the stationary portion 40 according tothe present preferred embodiment includes a sleeve 41, a sleeve holder42, and a stator 43. The rotating portion 50 according to the presentpreferred embodiment includes a shaft 51 and a magnet 52.

The shaft 51 is arranged to extend along the central axis 9. The sleeve41 is a cylindrical member arranged to surround the shaft 51. The sleeve41 is arranged inside the sleeve holder 42, which is in the shape of acup. A gap between the shaft 51 and a combination of the sleeve 41 andthe sleeve holder 42 is filled with a lubricating oil. FIG. 3 is avertical cross-sectional view of the sleeve 41. Referring to FIG. 3, aplurality of dynamic pressure grooves 411 are defined in an innercircumferential surface of the sleeve 41. Once the shaft 51 startsrotating, a dynamic pressure is induced in the lubricating oil by thedynamic pressure grooves 411. A force to support the shaft 51 is thusincreased.

That is, the motor 20 according to the present preferred embodimentincludes a fluid dynamic bearing defined by the inner circumferentialsurface of the sleeve 41, which is a stationary bearing surface providedin the stationary portion 40, an outer circumferential surface of theshaft 51, which is a rotating bearing surface provided in the rotatingportion 50, and the lubricating oil arranged between the innercircumferential surface of the sleeve 41 and the outer circumferentialsurface of the shaft 51. The dynamic pressure grooves 411 may be definedeither in the inner circumferential surface of the sleeve 41 asillustrated in FIG. 3, or in the outer circumferential surface of theshaft 51.

The stator 43 includes a stator core 431 and a plurality of coils 432.The stator core 431 is fixed to an outer circumferential surface of thesleeve holder 42. In addition, the stator core 431 includes a pluralityof teeth 433 arranged to project radially outward. The stator core 431is defined by, for example, laminated steel sheets, each of which is amagnetic body. Each coil 432 is defined by a conducting wire woundaround a separate one of the teeth 433. Note that the stator core 431may be fixed to the base portion 10 directly or indirectly with anothermember intervening therebetween.

The impeller 30 is a rotating body arranged to rotate together with theshaft 51 to produce an air current traveling in a centrifugal direction.FIG. 4 is a top view of the impeller 30. Referring to FIGS. 1, 2, and 4,the impeller 30 according to the present preferred embodiment includes aresin portion 31 and a metal plate 32. The resin portion 31 includes ablade support portion 311 and a plurality of blades 312. The bladesupport portion 311 is arranged to extend radially outward from acircumference of an upper end portion of the shaft 51. An innercircumferential portion of the blade support portion 311 may be eitherdirectly fixed to the shaft 51 or indirectly fixed to the shaft 51 withanother member intervening therebetween. The blades 312 are arrangedradially outside of the blade support portion 311, and are arranged atregular intervals in the circumferential direction. Each blade 312 isarranged to extend obliquely with respect to both a radial direction andthe circumferential direction. Note that the blades 312 may notnecessarily be arranged at regular intervals in the circumferentialdirection. That is, the blades 312 may alternatively be arranged atirregular intervals in the circumferential direction.

The metal plate 32 is an annular metallic member arranged below theblades 312. The metal plate 32 according to the present preferredembodiment is produced by subjecting a flat metal sheet to pressworking. Aluminum or an aluminum alloy, for example, is used as amaterial of the metal plate 32. Note that the metal plate 32 mayalternatively be made of a metal other than aluminum and the aluminumalloy.

FIG. 5 is a top view of the metal plate 32. Referring to FIGS. 2 and 5,the metal plate 32 according to the present preferred embodimentincludes a flat plate portion 321 and a plurality of inclined portions322. The flat plate portion 321 is annular and is arranged to extendperpendicularly or substantially perpendicularly to the central axis 9.Each of the inclined portions 322 is arranged to obliquely extendradially inward and axially upward from a radially inner end portion ofthe flat plate portion 321. The inclined portions 322 are arranged atregular or substantially regular intervals in the circumferentialdirection. In addition, referring to FIG. 5, the flat plate portion 321includes cuts 323 each of which is recessed radially outward betweenadjacent ones of the inclined portions 322. Thus, when the metal plate32 is manufactured, the inclined portions 322 can be bent upward whilepreventing deformation of the flat plate portion 321.

As described above, at least a portion of the impeller 30 according tothe present preferred embodiment is made of a resin. The impeller 30 isthus reduced in weight when compared to the case where the entireimpeller 30 is made of a metal. In particular, the impeller 30 can befurther reduced in weight by reducing the thickness of the metal plate32. For example, the flat plate portion 321 of the metal plate 32 isarranged to have an axial thickness smaller than a radial thickness ofeach blade 312. Moreover, when a light metal, such as, for example,aluminum or an aluminum alloy, is used as the material of the metalplate 32, the impeller 30 can be further reduced in weight.

When the impeller 30 is manufactured, a molten resin is injected into amold for resin molding in which the metal plate 32 has previously beenplaced. Then, the molten resin injected into the mold is cured to definethe resin portion 31. In other words, an insert molding process isperformed. At this time, portions of the metal plate 32 are covered withthe resin of the resin portion 31. The resin portion 31 is thus fixed tothe metal plate 32. In particular, according to the present preferredembodiment, each of the inclined portions 322 of the metal plate 32 isheld from both sides both radially and axially by the resin of the bladesupport portion 311. This contributes to preventing the resin portion 31and the metal plate 32 from being separated from each other. Inaddition, the inclined portions 322 are each held from both sidescircumferentially by portions of the resin which are arranged betweenthe inclined portions 322. The resin portion 31 and the metal plate 32are thus prevented from turning circumferentially relative to each otherby portions of the resin which have flowed into the cuts 323. The resinportion 31 and the metal plate 32 are thus prevented from turningrelative to each other.

In addition, the resin portion 31 according to the present preferredembodiment includes an annular lower surface 313 arranged radiallyinside of the flat plate portion 321 of the metal plate 32. The lowersurface 313 of the resin portion 31 and a lower surface of the flatplate portion 321 are radially adjacent to each other and substantiallyflush with each other. In addition, the lower surface 313 of the resinportion 31 is arranged axially opposite to the upper surface of the baseportion 10 with a slight gap intervening therebetween. Provision of theannular lower surface 313 as described above increases the thickness ofthe blade support portion 311 when compared to the case where the lowersurface 313 is not provided. Thus, strength of the blade support portion311 is increased.

In addition, the magnet 52, which is annular, is fixed to the bladesupport portion 311 through a yoke 53 made of a magnetic material. Theyoke 53 is arranged radially outside of the magnet 52. An innercircumferential surface of the magnet 52 includes north and south polesarranged to alternate with each other in the circumferential direction.Note that a plurality of magnets may be used in place of the annularmagnet 52. In the case where the plurality of magnets are used, themagnets are arranged in the circumferential direction such that northand south poles alternate with each other.

Once electric drive currents are supplied to the coils 432, magneticflux is generated around each of the teeth 433 of the stator core 431.Then, a torque centered on the central axis 9 is produced by interactionbetween the magnetic flux of the teeth 433 and that of the magnet 52. Asa result, the rotating portion 50 of the motor 20 and the impeller 30are caused to rotate. Once the impeller 30 starts rotating, air is takeninto the case. 90 through the opening 91 defined in the case 90 asindicated by white arrows in FIG. 2. Then, the air taken into the case90 is discharged in the centrifugal direction through the outlet 111.

Referring to FIG. 2, a circuit board 60 is arranged below the baseportion 10. An electrical circuit on the circuit board 60 may be eithera circuit designed to supply the electric drive currents to the coils432 of the motor 20, or a circuit designed to implement functions of theelectronic device in which the fan 1 is installed. The circuit board 60according to the present preferred embodiment includes a heat source 61,which is an electronic component, such as, for example, a CPU. While thecircuit board 60 is operating, more heat is generated at the CPU than atany other portion of the circuit board 60. In other words, according tothe present preferred embodiment, the CPU is the main heat source 61while the circuit board 60 is operating.

FIG. 6 is a partial vertical cross-sectional view of the fan 1.Referring to FIG. 6, a thermal grease 62 having a high thermalconductivity is arranged between an upper surface of the heat source 61and a lower surface of the base portion 10. The heat source 61 and thebase portion 10 are thus arranged to be in thermal contact with eachother. In addition, referring to FIG. 6, the lower surface of the flatplate portion. 321 of the metal plate 32 and the upper surface of thebase portion 10 are arranged axially opposite to each other with aslight gap 70 intervening therebetween.

Heat generated at the heat source 61 is first transferred from the heatsource 61 to the base portion 10 through the thermal grease 62. Then,the heat radiates from the upper surface of the base portion 10 to betransferred to the metal plate 32 as indicated by thin broken linearrows in FIG. 6. In addition, as indicated by a thick broken line arrowin FIG. 6, the air current produced by the impeller 30 flows radiallyoutward along an upper surface of the flat plate portion 321 of themetal plate 32. This air current absorbs the heat from the metal plate32. Thus, the heat generated from the heat source 61 is efficientlydischarged to air.

According to the present preferred embodiment, an axial dimension d ofthe gap 70 between the upper surface of the base portion 10 and thelower surface of the metal plate 32 is arranged to be 200 μm or less atleast at a portion of the gap 70. When the upper surface of the baseportion 10 and the lower surface of the metal plate 32 are thus arrangedin close proximity to each other, the heat is efficiently transferredfrom the base portion 10 to the metal plate 32 through radiation.Accordingly, the heat generated from the heat source 61 is efficientlydischarged to an outside.

The axial dimension d of the gap 70 is preferably arranged to be 150 μmor less at least at a portion of the gap 70, to further increaseradiation efficiency. Further, the axial dimension d of the gap 70 ismore preferably arranged to be 100 μm or less at least at a portion ofthe gap 70. Furthermore, efficiency in radiation of heat from the baseportion 10 to the metal plate 32 can be further increased by arrangingthe axial dimension d of the gap 70 between the upper surface of thebase portion 10 and the lower surface of the metal plate 32 to be 200 μmor less, 150 μm or less, or 100 μm or less through the entire gap 70.

Aluminum or the aluminum alloy is preferably used as the material ofeach of the base portion 10 and the metal plate 32. Use of aluminum orthe aluminum alloy, each of which has a high thermal conductivity,contributes to efficient transfer and radiation of the heat generatedfrom the heat source 61. Heat dissipation efficiency can thus be furtherincreased.

In addition, the metal plate 32 according to the present preferredembodiment is arranged to continuously extend in an annular shape aroundthe central axis 9. Thus, heat stored in the base portion 10 can beemitted to air all around the central axis 9. The heat dissipationefficiency can thus be further increased.

In addition, referring to FIG. 6, according to the present preferredembodiment, at least a portion of the heat source 61 and at least aportion of the flat plate portion 321 of the metal plate 32 are arrangedone over the other in the axial direction. When the heat source 61 andthe metal plate 32 are arranged to have, such a positional relationship,a proportion of the amount of heat which is transferred from the heatsource 61 to the metal plate 32 through the base portion 10 can beincreased. Accordingly, the heat generated from the heat source 61 canbe more efficiently discharged to the outside.

In particular, according to the present preferred embodiment, a centerof the heat source 61 and the flat plate portion 321 of the metal plate32 are arranged to axially overlap with each other. When the heat source61 and the metal plate 32 are arranged to have such a positionalrelationship, the proportion of the amount of heat which is transferredfrom the heat source 61 to the metal plate 32 through the base portion10 can be further increased. Accordingly, the heat generated from theheat source 61 can be more efficiently discharged to the outside.

In addition, referring to FIGS. 4 and 6, according to the presentpreferred embodiment, a radially outer end portion of each blade 312 anda radially outer edge of the metal plate 32 are arranged atsubstantially the same radial position. This enables air currentsgenerated by the blades 312 to flow along an entire upper surface of themetal plate 32. Thus, heat stored in the metal plate 32 can be moreefficiently discharged to the air.

In addition, as described above, the fluid dynamic bearing is used inthe motor 20 according to the present preferred embodiment. Use of thefluid dynamic bearing contributes to reducing a vertical movement of theimpeller 30 when compared to the case where another type of bearing isused instead. Therefore, the upper surface of the base portion 10 andthe lower surface of the flat plate portion 321 can be arranged in closeproximity to each other while preventing a contact between the baseportion 10 and the flat plate portion 321 of the metal plate 32. Theclose proximity of the upper surface of the base portion 10 to the lowersurface of the flat plate portion 321 contributes to increasing theamount of radiant heat transferred from the base portion 10 to the flatplate portion 321. As a result, the heat generated from the heat source61 can be more efficiently discharged to the outside.

In addition, according to the present preferred embodiment, while mostof the impeller 30 is defined by a resin molding process, a surface ofthe impeller 30 which receives the radiant heat is made of not a resinbut a metal. In this case, flatness of the surface which receives theradiant heat can be maintained even if a portion of the resin portion 31is deformed by, for example, effect of thermal contraction during theresin molding process. Accordingly, the surface is able to stablyreceive the radiant heat from the base portion 10.

While preferred embodiments of the present invention have been describedabove, it will be understood that the present invention is not limitedto the above-described preferred embodiments.

FIG. 7 is a partial vertical cross-sectional view of a fan 1A accordingto a modification of the above-described preferred embodiment of thepresent invention. Similarly to the impeller 30 according to theabove-described preferred embodiment, an impeller 30A of the fan 1Aillustrated in FIG. 7 includes a resin portion 31A and a metal plate32A. However, in the modification illustrated in FIG. 7, a blade supportportion 311A of the resin portion 31A is not arranged to extend up tothe metal plate 32A. Accordingly, the resin portion 31A according to themodification illustrated in FIG. 7 includes a through hole 314A arrangedto pass therethrough in the axial direction radially inside of the metalplate 32A and radially outside of the blade support portion 311A.

Once the fan 1A according to the modification illustrated in FIG. 7 iscaused to rotate, a portion of air which is sucked from a space abovethe impeller 30A due to blades 312A passes through the through hole 314Ato strike an upper surface of a base portion 10A. Accordingly, a portionof heat stored in the base portion. 10A is emitted to air without beingtransferred to the metal plate 32A through radiation. That is, the fan1A illustrated in FIG. 7 includes a first heat dissipation channel,through which heat is emitted from the base portion 10A to the airthrough the metal plate 32A, and a second heat dissipation channel,through which heat is directly emitted from the base portion 10A to theair. Such emission of heat through a plurality of heat dissipationchannels may lead to an additional increase in the heat dissipationefficiency.

FIG. 8 is a vertical cross-sectional view of a fan 1B according toanother modification of the above-described preferred embodiment of thepresent invention. The fan 1B illustrated in FIG. 8 includes a cover12B. The cover 12B is arranged to extend perpendicularly to a centralaxis 9B above an impeller 30B. In addition, a housing to accommodate theimpeller 30B is defined by a base portion 10B, a side wall portion 11B,and the cover 12B. An inlet 121B for gas is defined in a center of thecover 12B. Once the impeller 30B is caused to rotate, air is taken intothe housing through the inlet 121B from a space above the cover 12B.Then, the air is accelerated by the impeller 30B, and is discharged in acentrifugal direction through an outlet 111B.

FIG. 9 is a vertical cross-sectional view of a fan 1C according to yetanother modification of the above-described preferred embodiment of thepresent invention. In the modification illustrated in FIG. 9, a heatsource 61C, which is a heat source, is arranged at a position away froma base portion 10C. A lower surface of the base portion 10C and the heatsource 61C are connected to each other through a heat pipe 63C. The baseportion. 10C and the heat source 61C, which is a heat source, are thusarranged to be in thermal contact with each other. Heat generated at theheat source 61C is transferred to the base portion 10C through the heatpipe 63C. Then, radiant heat is transferred from the base portion 10C toa metal plate 32C, and the heat is discharged to air. As describedabove, the heat source may not necessarily be arranged on the lowersurface of the base portion.

Note that, although the heat source is the CPU according to theabove-described preferred embodiment, heat sources according topreferred embodiments of the present invention are not limited to CPUs.For example, heat sources according to preferred embodiments of thepresent invention may be other electronic components which, whenenergized, generate heat, such as switching elements or resistors.

Also note that details of the structure and the shape of a fan accordingto a preferred embodiment of the present invention may differ fromdetails of the structure and the shape of each fan as illustrated in theaccompanying drawings of the present application. Also note thatfeatures of the above-described preferred embodiments and themodifications thereof may be combined appropriately as long as noconflict arises.

Preferred embodiments of the present invention are applicable tocentrifugal fans.

What is claimed is:
 1. A fan comprising: a motor arranged to produce atorque centered on a central axis extending in a vertical direction; animpeller arranged to rotate through the torque to blow air in acentrifugal direction; a metallic base portion arranged to extendperpendicularly to the central axis below the impeller to support themotor, the impeller rotating with respect to the base portion; and aheat source arranged to be in thermal contact with the base portion;wherein the impeller includes: a resin portion including a blade supportportion directly or indirectly fixed to a rotating portion of the motor,and a plurality of blades arranged radially outside of the blade supportportion; a metal plate having a ring shape including an inner part and aflat plate portion provided circumferentially outside the inner part,the metal plate being attached to the plurality of blades such that alower surface of the flat plate portion and an upper surface of the baseportion are arranged axially opposite to each other with a gap, theinner part being covered with a resin of the resin portion; and an axialdimension of the gap is arranged at least at a portion of the gap,wherein the inner part is an inclined portion arranged to extendradially inward and axially upward from a radially inner end portion ofthe flat plate portion; and wherein each inclined portion is held fromboth sides both radially and axially by a resin of the blade supportportion.
 2. The fan according to claim 1, wherein the axial dimension ofthe gap is arranged through the entire gap.
 3. The fan according toclaim 1, wherein the metal plate is arranged to continuously extend inan annular shape around the central axis.
 4. The fan according to claim1, wherein the metal plate includes a plurality of inclined portionsarranged in a circumferential direction.
 5. The fan according to claim4, wherein the flat plate portion includes cuts each of which isrecessed radially outward between adjacent ones of the plurality ofinclined portions.
 6. The fan according to claim 1, wherein the heatsource is arranged below the base portion; and at least a portion of theheat source and at least a portion of the flat plate portion of themetal plate are arranged one over the other in the axial direction, andare arranged to be in thermal contact with each other.
 7. The fanaccording to claim 6, wherein a center of the heat source and the flatplate portion of the metal plate are arranged to axially overlap witheach other, and are arranged to be in thermal contact with each other.8. The fan according to claim 1, wherein a radially outer end portion ofeach blade and a radially outer edge of the metal plate are arranged atsubstantially a same radial position.
 9. The fan according to claim 1,wherein the resin portion includes a lower surface arranged opposite tothe upper surface of the base portion and radially inside of the lowersurface of the flat plate portion.
 10. The fan according to claim 1,wherein the flat plate portion is arranged to have an axial thicknesssmaller than a radial thickness of each blade.
 11. The fan according toclaim 1, wherein the metal plate is made of aluminum or an aluminumalloy.
 12. The fan according to claim 1, wherein the motor includes: astationary portion fixed to the base portion, and including a stationarybearing surface; and the rotating portion arranged to rotate togetherwith the impeller, and including a rotating bearing surface; thestationary bearing surface of the stationary portion and the rotatingbearing surface of the rotating portion are arranged opposite to eachother with a lubricating oil intervening therebetween; and one of thestationary bearing surface and the rotating bearing surface includes adynamic pressure groove arranged to induce a dynamic pressure in thelubricating oil.
 13. The fan according to claim 1, wherein the resinportion includes a through hole arranged in an axial direction radiallyinside of the metal plate.
 14. The fan according to claim 1, furthercomprising a side wall portion arranged to extend in a circumferentialdirection radially outside of the impeller, wherein an outlet is definedbetween both circumferential end portions of the side wall portion; theimpeller is arranged to produce an air current to be discharged in thecentrifugal direction through the outlet; and the side wall portionincludes a guide projection arranged to project between the impeller andthe outlet.
 15. The fan according to claim 1, wherein an upper surfaceof the inner part and a lower surface of the inner part are covered withthe resin of the resin portion.